Triple gate



Oct. 25, 1949. c. w. JOHNSTONE ET AL 2,485,386

TRIPLE GATE 5 Sheets-Shet 1 Filed Feb. 21, 1946 TRANSMITTER TRANSMITTER III IE L

GATING SWITCH TRIGGER CIRCUIT CODE RADAR TRIGGERS awe/Mow CHARLES W. JOHNSTONE LEONARD P. MAUTNER c. w. JOHNSTONE ETAL 2,485,886

Oct. 25, 1949.

TRIPLE GATE Filed Feb. 21, 1946 3" Sheets-Sheet 2 @wwwbo'w CHARLES W. JOHNSTONE LEONARD P. MAUTNER Patented Oct. 25, 1949 UNITED STATES PATENT OFFICE TRIPLE GATE Navy Application February 21, 1946, Serial N 0. 649,417

3 Claims. (01. 250-27) This invention relates to a transmission system in which a plurality, greater than two, of difierent kinds of transmission means are caused to emit their individually distinctive signals in time sharing fashion.

It is an object of this invention to produce a time shared transmission system in which at least three transmission means are caused to send out their individually distinctive signals in time sharing fashion, the operation being controlled bya novel gating switch having a number of output terminals equal to the number of transmission means to be controlled. On each terminal appears, in rotative time sequence, a gating signal which permits operation of the associated transmitting means for a predetermined time interval, following which the gating signal is transferred to an adjacent terminal. Transferring of the signal is repeated in rotative succession.

' It is another object of this invention to produce a time shared transmission system in which at least three transmission means are caused to operate intermittently in rotative succession, by the operation of an electronic gating switch having a number of switching means corresponding to the number of transmission means. Each switching means comprises a stable electronic multivibrator operable, upon reception of a proper triggering signal, between two discrete conditions.

It is a further object of this invention to produce a gating switch comprised of at least three switching means, each operable between two discrete conditions, and so arranged that upon operation of one of the switching means, an adjacent switching means automatically operates to its other discrete position, the operations being initiated by a switch triggering signal applied indiscriminately to each of the switching means.

In accordance with these objects and with other objects which will become apparent in the specification, the time shared transmission system and gating switch of this invention will be described with reference to the accompanying drawings in which,

Fig. 1 shows in block diagram form a first embodiment of the transmission system of this invention;

Fig. 2 shows a. more detailed and complicated embodiment, also in block diagram form;

Fig. 3 shows schematically an electronic gating switch forming part of this invention and constituting one of the elements of the time shared transmission system of this invention; and

Fig. 4 shows a complete circuit diagram of the gating switch shown schematically in Fig. 3.

Referring to Fig. 1, there is shown a block diagram of a time shared transmission system comprising, in this embodiment, three transmission means l0, II and I2, each efiective, when properly gated, to produce a distinctive and characteristic signal, shown by the numerals I, II and III. It is desired that the distinctive signal producers share transmission time in rotative succession, so that during an extended interval of time each of the three signals may be sent over a single transmission channel.

In order to permit time sharing among three or more individually distinctive transmission means, a novel gating switch I? has been devised having a number of output terminals equal to the number of transmission means to be controlled, in this case three, as shown at I4, I5, and Hi. In the operation of gating switch IS, a number of periodically repeated switch triggering signals 20, derived from a trigger circuit 2|, are applied at the single input terminal 22 of the gating switch [3, and at terminals l4, l5, and 16 appear gating signals I, II, and III, respectively. The gating signals, it will be noted, share time; so that with termination of gating signal I, initiated by one of the signals 20, gate II appears on terminal 15; and with its termination, also initiated by a signal 20, gate III appears on terminal IS. with the termination of gate III, gate I reappears and the cycle is reinitiated in rotative succession.

Gating switch l3 consists essentially of three switching means connected, respectively, to terminals l4, l5 and i6, and operating between two discrete conditions, one of said conditions producing the gating signal necessary to permit signal production by the associated transmission means I 0, i i, or l2. As will be explained more fully hereinafter, each of the switching means comprising the gating switch I3 is interconnected to an adjacent switching means; so that when the first mentioned switching means terminates its gating signal, the next adjacent switching means starts its gating signal, and so on in rotative succession. As mentioned hereinbefore, the particular moment when one gate terminates and the adjacent gate begins is determined by the switching impetuses or switch triggering signals 20.

The time shared transmission system described broadly above and illustrated in Fig. 1 is particularly adaptable to an identification system assowhich the first interrogating transmission, with its particular coding, is sent out for arfirst interval, followed successively by the second and third interrogating transmissions, the process being repeated in rotative succession. The gating signals must be of short duration, in;order'that substantially continual maintained at all times.

A system for attaining this object is shown in Fig. 2, wherein 23 designates a modulator-transmitter, which emits signals on a single carrier frequency, the characteristic of the envelope of transmission being determined by the nature of the modulating code I, II, or III, applied to modulator-transmitter 23. Modulating code generators 24', 25, and 2B are capable ofgenerating modulating pulses for transmitter 23, each code being individually distinct from the others, as shownat 30,3l, and 32. In order to accomplish the hereinbefore described time sharing, it is necessary that each of'the code generators 24, 25, and 26 send forth modulating pulses only during its preassigned portion of the cycle. To this end, the gating switch 13 described above in connection with Fig. l is employed to apply at each of its terminals I4, 15, andwlfi. a gating signal permitting; time sharing operationof the three code generators 24, 25, and 26. The switch triggering signals are obtained in this case, from a counting down circuit 33, which selects every Nth trigger in a series of input radar triggers 34, and derives therefrom the switch triggering signals 20.

The operation of the system of Fig. 2 is as follows. Periodically repeated radar triggers 34, synchronized with the search radar pulses, are counted down in circuit 33. Every Nth radar trigger (illustrated in this case as-every fourth trigger) emerges asoa switch triggerin signal 20. Signals 20 are applied simultaneously to each of theswitching means comprising gating switch l3 and produce in rotative succession the output gates I, II, and III on terminals 14, I5, and I6, respectively. These gates permit operation of the code generators 24, 25, and 26, so that the modulating codes 30, 3|, and 32 are emitted during the respective on periods of code generators 24, 25, and 26. The three codes 30, 3|, and 32 modulate the modulator-transmitter 23 and emerge as the envelopes of the'pulsed transmisinterrogation may be sions shown at they may beapplied to an antenna 30 or to any suitable transmissionchannel.

Gating switch I3 is shown more particularly in the schematic diagram of Fig. 3, wherein three pairsof tubes, 40a4|lb, Ma -Mb, and 42a-42b are illustrated schematically in a ring form of diagram. Each of the pairs of tubes Mal-40b, 4la.4|b, and 42a42b is connected as a stable. multivibrator, shown symbolically by the crossed. Mar-40b,

.4 pair is conducting, thereby holding the other tube non-conducting. A triggering signal applied to the multivibrator initiates a change in the condition of the multivibrator either by turning on the non-conducting tube or by turning off the conducting tube. The action started by the trigger is rapidly intensified by operation of the cross connection between the tubes; and the tube which was previously non-conducting goes into conduction, holding the other tube in a non-conductive condition. The multivibrator is then quiescent until another triggering signal is applied.

Each of the switching means, or multivibrators, shown consists of an a tube and a b tube. It will be noted that the output from each of the 1) tubes; 40?), 41b and 42b is applied to the input of the b tube next adjacent in rotative succession. Specifically, the anode of tube 4!!) is connected to the grid of tube 4% by capacitor 44; th anode of tube 401) is connected to'the grid of tube 42b by capacitor 45; and the anode of tube 42b is connectedxto the grid of'tube MI) by capacitor 46, thuscompleting the cycle of connections. It will be understood that anysuitable form of circuit means may be employed to connect the output of a given I) tube to the input of the next succeeding 1) tube. From the anodes of the respective b tubes, 40b, 41b, and 421:, the gating switch output is taken, at terminals l5,

l4, and iii, respectively The input to the. gating, switch is in the form of a negative trigger signal. 2H, applied at terminal 22 connected to the grid.

of each of the a tubes, 40a, ram, and 42a, through capacitors 50, 5!, and 52, respectively..

It will be seen that the gating switch above described consists of three switching means, each in the form of a stable multivibrator operating.

negative trigger signals indiscriminately to the.

input of each of the a tubes.

The operation of the gating switch of Fig. 3 will now be described. With the application of anode voltages and grid biases to thecircuit, one of the tubes of each pair will tend to assume conduction, producing a voltage holding the other tube in a non-conductive state. Although each of the six tubes is of the same type, assume that manufacturing discrepancies in the circuit cause tube 421) to start conduction a moment before the other tubes start conduction. Conduction in 421) will cause its anode to assume'the lower voltage of its two discrete conditions, and will place a negative going signal on the grid of 4H) through capacitor 46. This will block conduction in Mb; Tube 412) going off will cause its anode to assume its positive condition, transferring a positive going voltage through capacitor 44 to the grid of 402). This willdrive 401; into conduction and will place anegative going signal on its anode, which will be translated through capacitor 45 to the grid "of 42b; Since it has been assumed that 4212 initiated the cycle of conduction, it will continue to conduct in spite of the negative signal. The above initial operation will thus place the six tubes in one oithe twoconditions, off. or on, as shown in the explanatory circles surrounding thecircuitdiagram of Fig. 3. Thusstep I finds 41b oiT, with 40b and '42b on; and the a tubes in a condition opposite to that of their associated b tubes. It is possible that the initial condition might be otherwise, in which case the circuit would not be prepared to commence its normal cyclic operation. This contingency will be provided for by the inclusion of a self starter tube, to be described in connection with the complete circuit shown in Fig. 4.

With the tubes in the conditions shown in ring I, a negative switching impetus or switch triggering signal 20 is applied through terminal 22 to the grid of each of the a tubes, 40a, Ma, and 42a. Inasmuch as both 52a and 40a are off, the only tube which will be afiected by the negative trigger is Me, which will begin to stop its conduction. The conventional multivibrator action, represented by the cross connecting circuits 43, will intensify the blocking of 41a, so that 4 lb will come on while 4la will go completely 011. Turning on, i. e., starting conduction, of 4H) will place a negative going signal on the input of 40b, through the circuit means (in the form of capacitor 44) connecting the output of 4th with the input of 4017. Tube 40b, which in step I was on, will be turned ofi, and multivibrator action will turn 40a on. Turning oil of 40b will place a positive going voltage on its anode, but this will not affect 42b inasmuch as it is already in a conducting, or on, condition. It will thus be seen that the high voltage condition existing at the anode of an ofi tube has been transferred from 4") in step I, as denoted by arrow 54, to the anode of 40b in step II, as denoted by arrow 55. In the meantime, the multivibrator 42a42b has been unafiected by the change from step I to step II.

The succeeding negative trigger 20 will act in a similar manner on the a tube which is on, in this case 40a; and the high voltage condition represented by an off 22- tube will be transferred from 401) to 4217, while multivibrator 4la4lb will be unafiected. In this manner, the off conditlon for the b tube is transferred in rotative succession around the ring by each negative trigger an applied to the grid, or input circuit, of each a tube.

It will be readily apparent that any number of pairs of tubes connected in multivibrator fashion may be utilized in such a ring circuit as shown in Fig. 3. Furthermore, if desired, triggers 20 may be positive instead of negative, in which case the non-conducting a tube will be the one aflected.

Summarizing, it will be seen that the circuit of Fig. 3 comprises a plurality of switching means, to each of which is applied indiscriminately a switch triggering signal, but only one of which is in a condition at any one time to respond to the signal. Response of the conditioned switching means, causing it to operate to the second of its discrete conditions, causes operation of the next succeeding switching means in cyclic succession; but operation of the last mentioned switching means is not transmitted further to the succeeding switching means in the ring. The last mentioned switching means then becomes conditioned to be responsive to the next succeeding switch triggering signal, and so on around the ring as long as switch triggering signals are received.

From the above described operation of the circuit of Fig. 3, it is apparent how the gating signals appearon the terminals I4, l5, and iii of Figs. 1, 2, and 3. These gating signals, represented by the positive blocks I, II, and III, correspond with the ofi condition of the several b 6 tubes, which condition is shifted in rotatlve succession around the ring.

The circuit shown schematically in Fig. 3 is shown in detail in Fig. 4 and includes, in addition, a pair of trigger tubes, one being the normal trigger tube, and the other being the selfstarting trigger tube, mentioned hereinbefore, which is needed if the initial conditions, when the circuit is first energized, are not such as to make an a tube receptive to the negative triggers 20.

Referring to Fig. 4, the circuit has been shown with the three multivibrators Mia-40b, Ma,- 4lb, and 42a-42b, designated with the same reference numerals as in Fig. 3. The stable multivibrator cross connection 43 has been shown in the form of D. C. coupling resistors 60 in parallel with capacitors 6|. The anodes of each of the tubes are taken to ground through conventional load resistors 62, while the oathodes have been connected to a source of volts. The grids are returned to 2l0 volts through resistors 63. The grids of each of the a tubes are triggered through a normal trigger tube 64 having plate load resistor 65. Normal, steady-state operation of the circuit of Fig. 4 is as described for the circuit of Fig. 3, with positive input triggers being applied to tube 64, in which they are amplified and inverted to form the negative triggers 20 applied to the grids of the (1 tubes.

It is possible that the initial application of potential might be followed by the multivibrators assuming such a condition that each of the a tubes is non-conducting, or oil. In this event, the negative triggers 20 would not affect any of the a grids; and the circuit would remain quiescent.

To obviate this difiiculty, a self-starting trigger tube 10 is provided, to which positive input triggers are applied in parallel with tube 64. When the gating switch is operating normally, the average potential on conductor H, which is connected to the respective anodes of the a tubes through the three resistors 12. is sufliciently low to bias tube 10 below out 01f. Since conductor H is connected to grid 13 of tube 10, this tube will, during normal operation of the gating switch, be completely inoperative by virtue of the below-cut-off bias on its grid. If the undesirable condition is encountered in which all a tubes are non-conducting, the average D. C. potential 0n conductor H will be raised sufliciently to bring the bias on the grid of tube 10 into the operating region. Hence, the positive input triggers applied at terminal 15 will be translated and amplified through tube 10, and will appear on the anode of tube NJ as negative switch triggering signals. These signals will be translated through capacitor 16 and the first R. C. circuit 606l to the grid of tube 40b. Since it has been assumed that 400. was non-conducting and 40b conducting, this negative signal will cause 40b to cut ofi, turning on 40a. Conduction in 40a will lower the average potential on conductor H and grid 13 to the point where tube ill is inoperative. Inasmuch as 40a is conducting, and therefore receptive to negative triggers, the circuit is now in a normal condition, ready to receive triggering signals 20 from tube 64. Self-starting tube 10 drops out of the picture, and the circuit continues normal switching operation with the reception of each positive input trigger on terminal 15.

The gating switch illustrated in Figs. 3 and 4,

andcsdesc'ribed immediately above, issuitable. ,for:

any application where it is desired to have a gating: signal appear in ,rotative' succession onone :of a plurality of output terminals; in'res'ponse 'to triggering 'signals'applied'to the input of the-gating switch;

whilezthis inventionshould not be limited to anyspecific circuit constants, the. following are giveniasi illustrative of values of. circuit com.-

ponents whichmay be utilized'in the circuitof Fig. 4.

Although we have shown'and described certain specific: embodiments of the invention, we are fully; aware of the many modifications possible thereof. This invention is not to be restricted except insofar as is necessitated by prior art and the spirit of the appended claims.

Weclaim-z 1. An electronic switching circuit comprising a plurality of pairs of tubes, each pair comprising a first tube and a second-tube having separate inputs'andoutputsinterconnected as a trigger circuit'h'avingtwo alternative stable states, circuit means connecting the output of the first tube of each'of said pairs to the input of the first tube of another of said pairs, trigger signal input means connected to the input of the second tube of each of said -pairs;'anda normally inoperative triggering tubehaving an input connected to the output of the second'tub'e of each of said pairs and an output'connected to the input of the firsttube of one of said pairs, said triggering tube'being operative in response to'a predetermined condition in said second tubes, to apply a switchtriggering signal to the input of the first tube of said one of said pairs.

2'.- An electronic switching circuit comprising a plurality ofipairs of tubes having at least cathode,

anode; and control grid electrodes, each pair comprising afirst tube and a second tube interconnected as a trigger circuit having'two alternative stable-states; first circuit means connecting the anode of the first tube of each of said pairsto the control grid of the first tube of another of said pairs,- trigger signal means, second circuit means connecting said trigger signal means to the control grid of the second tub'eof each of said pairs,

a'self-starting means including a trigger tubehav ing at.least a cathode, an anode, anda control. grid, separate impedance means respectively con meeting the anode of each of said second tubes-to the control grid of said trigger tube, and third circuit means connecting the anode of said trigger tube to the control grid of a first tube of one of said pairs of tubes, said self.-starting means operative responsive to a predetermined state inv each of said second tubes to change the state of said one pair of tubes.

3; An electronic switching circuitv comprising, a

plurality of pairs of tubes having at least cathode;

anode, and control gridfelectrodes, each pair com prising'a first'tub'e and a second tube interconnected as a trigger circuit having two alternative stable states, first circuit means connecting the anode of the first tube ofeach of said pairs to the control grid of the first tube of another of 'sald pairs, trigger signal means, second circuit means 1 connecting said trigger signal means to the control:-

grid of the second tube of each of said pair's, a self starti'ng means including a trigger tubeliaving at least a cathode, an anode, and a control grid, separate impedance means respectively 0011' ne'cting the anode of each of said second tubes to the control grid of said'trig'ger tube, fixed biasing means connected to the cathode of said trigger tube operative to render said trigger-tube non-conducting when any of said second REFERENCES CITED The following references are of record in the file of this. patent:

UNITED STATES PATENTS Numbervv Name" Date. 1,873,785 Ranger Aug; 23, 1932 1,914,407 Demarest June 20', 1933 1,951,524 Nicolson Mar. 20, 1934' 1,956,397 Nicolson Apr; 24; 1934 2,136,621 King et a1 Nov. 15, 1938" 2,146-,862 Shumard Feb. 14, 1939 2,369,662 Deloraine Feb; 20, 1945 2,404,918 Overbeck July 30, 1946" 2,405,930 Goldberg Aug. 13, 1946 2,406,165 Schroeder Aug. 20, 1946: 2,406,760 Goldmark Sept. 3, 1946 2,426,454 Johnson Aug, 26, 1941 2,435,207 Dimond Feb. 3, 1948. 2,444,950 Nichols July 13, 1948 

